Liquid crystal display device

ABSTRACT

A liquid crystal display device sandwiching liquid crystal between a TFT substrate having a rectangular plane and an opposing substrate having a rectangular plane, wherein a long side of the TFT substrate is longer than a long side of the opposing substrate, the long side of the opposing substrate is formed with a chamfer, and a light shielding film made of metal is formed on the TFT substrate around a position corresponding to the center of the long side of the opposing substrate. By using the light shielding film, the chipping condition of the opposing substrate near the chamfer can be accurately and rapidly evaluated.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/845,437, fled on Oct. 17, 2013, which claims priority from Japaneseapplication JP 2012-091466 filed on Apr. 13, 2012, the contents of whichare hereby incorporated by reference into this application.

FIELD OF THE INVENTION

The present invention relates to a display device, and specifically to aliquid crystal display device with an improved bending strength of aliquid crystal display panel.

BACKGROUND OF THE INVENTION

A liquid crystal display device is provided with a TFT substrateincluding a pixel electrode and a thin film transistor (TFT) in a matrixform and an opposing substrate opposing the TFT substrate and formedthereon with a color filter or the like in a position corresponding tothe pixel electrode of the TFT substrate, and liquid crystal issandwiched between the TFT substrate and the opposing substrate. Thedevice forms an image by controlling a light transmission of a liquidcrystal molecule with respect to each pixel.

For such a liquid crystal display device, there is a demand for reducingan external size of the set while retaining a certain size of a screenas well as for reducing a thickness of the liquid crystal display panel.However, reduction in the thickness of the liquid crystal display panelmay lead to a problem of its bending strength. Especially, a system ofcontrolling a display on a screen by pressing a finger or the like on atouch panel has been increasingly used in recent years. In such asystem, the bending stress is applied to the liquid crystal displaypanel through the touch panel.

When the bending stress is applied to the liquid crystal display panel,if there is a chip of glass or the like at an edge of the TFT substrateor the opposing substrate which are glass substrates, the glass maybreak from that point. In order to prevent this, the edge of the glasssubstrate is chamfered off. However, chamfering off alone cannotnecessarily provide a glass substrate with reliably high bendingstrength.

Japanese Unexamined Patent Application Publication No. 2011-84453describes a configuration of a chamfered glass substrate with aninclination root mean square of a roughness curve of the chamferedsurface RΔq being 0.1 or less to prevent a crack of the glass when aflexure is caused in the glass substrate. Japanese Unexamined PatentApplication Publication No. 2008-266046 describes a configuration of aglass substrate having its edge chamfered off with the chamfering sizebeing 18 to 75 μm in a direction of the substrate thickness to make itdifficult for a crack to be caused in the glass substrate.

SUMMARY OF THE INVENTION

Chamfering the glass substrate such as the TFT substrate and theopposing substrate constituting the liquid crystal display panel mayimprove the bending strength, but hardly ensures a consistent strength.In order to ensure the bending strength in the total number of theliquid crystal display panels, the edge of the glass substrate needs tobe evaluated with the total number of the liquid crystal display panelsin a production line.

Although it is performed on and near the chamfered edge of the glasssubstrate using an optical system such as a camera, the measurementaccuracy has not been enough and the finished liquid crystal displaypanels have varied in bending strength.

It is an object of the present invention to achieve a liquid crystaldisplay device that enables an efficient and accurate evaluation of thebending strength in the production line. It is another object of thepresent invention to achieve a liquid crystal display device havingconsistent bending strength characteristics.

The present invention seeks to overcome the above problems, and some ofits specific means are described below.

(1) A liquid crystal display device sandwiching liquid crystal between aTFT substrate having a rectangular plane with a TFT and a pixelelectrode formed thereon in a matrix form and an opposing substratehaving a rectangular plane with a color filter formed thereon, wherein along side of the TFT substrate is longer than a long side of theopposing substrate, the long side of the opposing substrate ischamfered, and the TFT substrate has a light shielding film made ofmetal formed thereon around a position corresponding to the center ofthe long side of the opposing substrate.

(2) A liquid crystal display device sandwiching liquid crystal between aTFT substrate having a rectangular plane with a TFT and a pixelelectrode formed thereon in a matrix form and an opposing substratehaving a rectangular plane with a color filter formed thereon, wherein along side of the TFT is longer than a long side of the opposingsubstrate, the long side of the opposing substrate is chamfered, a blackmatrix is formed in a position corresponding to the center of the longside of the opposing substrate, there is no chip on a top surface of theopposing substrate where a chamfer is formed in a predetermined regionon both sides of the center of the long side, and the predeterminedregion has a length of 1.3 mm along the long side of the opposingsubstrate and a length of 0.1 mm along a short side direction of theopposing substrate.

According to the present invention, it is possible to efficiently andaccurately evaluate a condition, such as a chip, of a glass substrateconstituting a liquid crystal display panel. Furthermore, because thetotal number of the liquid crystal display panels can be evaluated in ashort time, it is possible to perform the evaluation of the bendingstrength on the total number of liquid crystal display panels and alsoto provide the market with the liquid crystal display panels having areliably high quality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a liquid crystal display deviceaccording to the present invention;

FIG. 2 is an A-A cross-sectional view of FIG. 1;

FIG. 3 is a cross-sectional view showing a boundary portion of adjacentliquid crystal display panels on a mother substrate;

FIG. 4 is a perspective view of the liquid crystal display device beforechamfering and with a light shielding film formed thereon;

FIGS. 5A and 5B show an example of a chip caused by cutting the glassbefore chamfering or the like;

FIGS. 6A and 6B show an example of a chip caused when forming a chamfer;

FIG. 7 is a process flow showing steps before and after chamfering theliquid crystal display device;

FIG. 8 is a schematic view showing a method of evaluating an area aroundthe chamfer according to the prior art;

FIG. 9 is a schematic view showing a method of evaluating the areaaround the chamfer according to the present invention;

FIG. 10 is a perspective view of the liquid crystal display deviceshowing another side which can be chamfered;

FIG. 11 is a cross-sectional view of a normal chamfer;

FIG. 12 is a cross-sectional view showing an example of a modifiedchamfer;

FIG. 13 is a cross-sectional view showing another example of theboundary portion between the adjacent liquid crystal panels on themother substrate;

FIG. 14 is a cross-sectional view showing an example of a case in whicha black matrix is used as a light shielding firm for chamfer evaluation;and

FIG. 15 is a perspective view showing an example of a case in which theblack matrix is used as the light shielding film for the chamferevaluation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Details of the present invention will be described below with referenceto embodiments.

First Embodiment

FIG. 1 is a perspective view of a liquid crystal display deviceaccording to the present invention. Both terms “liquid crystal displaypanel” and “liquid crystal display device” may be used herein, which areinterchangeable. Such a liquid crystal display panel can be used, forexample, in a mobile phone and the like. In FIG. 1, an opposingsubstrate 200 formed with a color filter corresponding to each pixel isarranged in an opposing manner on a TFT substrate 100 on which pixelshaving a TFT and a pixel electrode are arranged in a matrix form. TheTFT substrate 100 and the opposing substrate 200 are bonded together bya peripheral sealing material, and liquid crystal is sandwiched by theTFT substrate 100 and the opposing substrate 200. The TFT substrate 100is formed to be larger than the opposing substrate 200, and a portionconsisting of the TFT substrate 100 alone is made to be a terminalportion 150.

In FIG. 1, two long sides of the opposing substrate 200 are chamfered.As will be explained later, because the chamfered portion has asignificant influence on the bending strength, it is required toevaluate a shape of the chamfer 10 in a production step. In order toperform the evaluation with high accuracy and at a high speed, accordingto the present invention, as shown in FIG. 1, an island of a lightshielding film 20 is formed on the portion corresponding to the centerof the long side of the opposing substrate 200. In FIG. 1, assuming thelength of the long side of the opposing substrate 200 as L, the centerof the island of the light shielding film 20 corresponds to the positionof L/2.

The island of the light shielding film 20 can be highly accuratelymeasured when the chamfer 10 is measured using a camera or the likeduring the step. The light shielding film 20 is formed on the TFTsubstrate 100, its position is at the center of the long side of theopposing substrate 200, and its size is defined by, for example, thewidth w along the long side of the opposing substrate 200 being 1.3 to2.6 mm and the depth v, that is the length in the direction of the shortside of the opposing substrate 200, being 0.1 to 0.2 mm. The lightshielding film 20 is arranged at the center of the long side of theopposing substrate 200 because the center receives the highest stresswhen the opposing substrate 200 is pressed.

The light shielding film 20 formed on the TFT substrate 100 is formed ofa metal film, because various metal films are formed on the TFTsubstrate 100 for use as a wire and an electrode, the light shieldingfilm 20 can be formed at the same time when one or more of the layersare patterned.

FIG. 2 is an A-A cross-sectional view of FIG. 1. In FIG. 2, the TFTsubstrate 100 and the opposing substrate 200 are bonded together by thesealing material 30. A liquid crystal 110 is sealed inside the sealingmaterial 30. There is a space outside of the sealing material 30, andthe island of the light shielding film 20 is formed on the TFT substrate100 side of this portion.

Although FIG. 1 shows an individual liquid crystal display panel,because it is not efficient to individually create separate liquidcrystal display panels, a mother panel arranged thereon with a largenumber of liquid crystal display panels is manufactured and then it isseparated into respective liquid crystal display panels by dicing,scribing, or the like. FIG. 3 shows a boundary portion betweenindividual liquid crystal display panels on such a mother panel. Theisland of the light shielding film 20 is formed on the boundary portionbetween the liquid crystal display panels including a separation line40.

FIG. 4 is a perspective view of the individual liquid crystal displaypanel separated from the mother substrate. The TFT substrate 100 and theopposing substrate 200 are not yet chamfered in FIG. 4. A chip of glassin the TFT substrate 100 or the opposing substrate 200 can occur duringscribing for separating each liquid crystal display panel and duringchamfering.

FIGS. 5A and 5B show a chip 50 caused during scribing or the like,wherein FIG. 5A is a top view of the chip portion and FIG. 5B is a B-Bcross-sectional view of FIG. 5A. The chip 50 in FIGS. 5A and 5B ischaracterized by being present both in the chamfer 10 of the opposingsubstrate 200 and on the top surface 210 of the opposing substrate.FIGS. 6A and 6B show the chip 50 caused during chamfering, wherein FIG.6A is a top view of the chip portion and FIG. 6B is a C-Ccross-sectional view of FIG. 6A. The chip 50 in FIGS. 6A and 6B ischaracterized by being present only on the top surface of the opposingsubstrate 200.

An influence on the bending strength of the opposing substrate 200 islargely affected by the chip 50 caused during chamfering, i.e. the chip50 present on the top surface of the opposing substrate 200. Therefore,it is necessary to incorporate a step of inspecting the shape of thechamfered portion into the manufacturing step.

FIG. 7 is a process flow of manufacturing the liquid crystal displaypanel according to the present invention. In FIG. 7, at Step A, during afilm formation on the TFT substrate 100, the island of the lightshielding film 20 is formed on the TFT substrate 100 for facilitating anevaluation of the chamfer 10. This is performed when a mother TFTsubstrate is formed. Subsequently the mother TFT substrate and a motheropposing substrate are bonded together to form the mother substrate.Then at Step B, the mother substrate is separated into the individualliquid crystal display panels by cell cutting. At Step C, the chamferingwork is then performed on each liquid crystal display panel.

After that, at Step D of determination, the chamfering work is evaluatedon all of the individual liquid crystal display panels. This step isperformed by, for example, evaluating an image of the top surface of theopposing substrate 200 corresponding to the portion with the chamfer 10using an inspection camera or the like. During this chamfer evaluation,an acceptable product is directed to Step E for cleaning and thendirected to a post-process. During the determination configuration D, arejected product is either chamfered again or discarded if it isdetermined to be beyond restoration.

FIG. 8 is a schematic view showing an outline of the inspection at StepD in FIG. 7 according to the prior art. In FIG. 8, the inspection camera300 is installed above the chamfer 10 of the opposing substrate 200 ofthe liquid crystal display panel, and this camera 300 is used to performthe inspection of whether there is the chip 50 on the top surface 210 ofthe opposing substrate 200 in the area around the chamfer 10.

In the prior art example shown in FIG. 8, there is no specific patternformed on a bottom surface of the opposing substrate 200 or the topsurface of the TFT substrate 100; an irregular pattern ca be formedthereon or an object can be reflected thereon. Thus, it is not possibleto achieve sufficient accuracy when measuring the top surface 210 of theopposing substrate 200 using the camera 300.

FIG. 9 is a schematic view showing an outline of the inspection at StepD in FIG. 7 according to the present invention. In FIG. 9, the opposingsubstrate 200 is formed with the chamfer 10, and the island of theshielding pattern 20 is formed on the top surface of the TFT substrate100. The size of the shielding pattern 20 is defined by, as explainedwith reference to FIG. 1, the width w in the side direction being 1.3 to2.6 mm and the depth v being 0.1 to 0.2 mm at the center of the longside.

The present invention is characterized in that no chip of glass ispresent on the top surface 210 of the opposing substrate 200, as shownin FIG. 6, in the region where the shielding pattern 20 is present.According to the present invention, with the presence of the shieldingpattern 20, the presence of the chip 50 on the top surface of theopposing substrate 200 around the chamfer 10 can be measured accuratelyand rapidly.

The chip 50 on the top surface 210 of the opposing substrate 200 ismeasured because the bending strength on the opposing substrate 200 ismost affected by the chip 50 present on the top surface 210 of theopposing substrate 200. The strictest specification is that there is nochip of glass in the island of the light shielding film, which is theinspection area, sized to 2.6 mm in the long side direction and 0.2 mmin the short side direction, namely the depth. The loosest specificationof the size of the island of the light shielding film 20, which is theinspection area, is characterized in that there is no chip 50 of glassin a range of 1.3 mm in the long side direction and 0.1 mm in the shortside direction, namely the depth.

Thus, at the center of the opposing substrate 200, by the fact thatthere is no chip of glass on the top surface 210 after chamfering, thebending strength of the opposing substrate 200 can be kept equal to orhigher than a predetermined value, and at the same time, the presence ofthe chip 50 on the top surface 210 after chamfering the opposingsubstrate 200 can be controlled.

FIG. 1 shows the case of forming the chamfer 10 on the long side of theopposing substrate 200. The chamfer 10 can be effectively formed notonly on the long side but also other sides of the opposing substrate 200or even on the sides of the TFT substrate 100. FIG. 10 shows the sideswhich can be formed with the chamfer 10 and also be effective with thechamfer 10. FIG. 10 shows the case of forming the chamfer 10 on foursides of the TFT substrate 100 and three sides of the opposing substrate200. The chamfer 10 is formed on seven sides in total.

In FIG. 10, the short side of the opposing substrate 200 facing aterminal portion 150 and the top surface of the TFT substrate 100 facingthe terminal 150 are not chamfered. This is because a sufficient anglecannot be spared for the chamfer due to the small thickness of theopposing substrate 200 of the liquid crystal display panel shown in FIG.10.

In FIG. 10, below the sides to be formed with the chamfer 10, the islandof the light shielding film 20 is formed during formation of the chamfer10 so that the chip on the top surface of the opposing substrate 200 andthat on the bottom surface of the TFT substrate 100 can be observedwell. For example, in order to efficiently evaluate the chamfer 10 onthe short side of the opposing substrate 200, the island of the lightshielding film 20 is formed in a corresponding portion of the TFTsubstrate 100. This enables an accurate and rapid evaluation of thechamfered portion as shown in FIG. 9.

Such an island of the light shielding film 20 can be shared by thechamfer evaluation of the opposing substrate 200 and the chamferevaluation of the TFT substrate 100. The sharing is possible only bychanging focal points of the camera 300. Although FIG. 10 shows thelight shielding film 20 in a case of forming the chamfer 10 on thebottom surface of the terminal portion 150 of the TFT substrate 100, itcan be replaced by the terminal made of the metal film formed on theterminal portion 150.

FIG. 11 is a cross-sectional view of the standard chamfer 10. In FIG.11, an angle θ of the chamfer 10 is 45 degrees, and a width d of thechamfer 10 is 15 to 50 μm. Variation in the bending strength increasesif the width d of the chamfer 10 is smaller than 15 μm, and the chip 50is more likely to occur on the top surface 210 of the opposing substrate200 if it exceeds 50 μm.

When the chamfer 10 is formed in this manner, if the chip 50 is causedon the top surface 210 of the opposing substrate 200 or the like, theproduct cannot be shipped due to its insufficient bending strength. FIG.12 shows an example in which the chip 50 has been removed from the topsurface 210 of the opposing substrate 200 by forming a further chamfer10 including the chip portion. In FIG. 12, the angle θ of the chamfer 10with respect to the top surface 210 is made smaller than 45 degrees.

FIG. 13 shows the boundary portion between two adjacent liquid crystaldisplay panels on the mother substrate. In the example shown in FIG. 13,the sealing material 30 is continuously formed between two adjacentliquid crystal display panels. In this case, as in FIG. 3, by formingthe island of the light shielding film 20 with a predetermined width onboth sides of the separation line 40, the evaluation of the chip 50after forming the chamfer can be performed simply and rapidly.

Although the sealing material 30 is formed over the light shielding film20 in FIG. 13, because the sealing material 30 is not perfectly black,the light shielding film 20 can be seen through the sealing material 30,and the chip 50 on the top surface 210 of the opposing substrate 200 andthe like can be reliably and efficiently measured as shown in FIG. 9 byusing the light shielding film 20.

FIG. 14 shows the boundary portion between the two adjacent liquidcrystal display panels on the mother substrate. In the example shown inFIG. 14, a black matrix 220 formed on the opposing substrate 200 isformed to continue with the two adjacent liquid crystal display panels.The black matrix 220 has the same effect as the light shielding film 20,the chip on the top surface 210 of the opposing substrate 200 in thechamfered portion can be evaluated using the black matrix 220 withoutotherwise forming the island of the light shielding film 20.

In the case of FIG. 14, however, because the black matrix 220 iscontinuously formed, an evaluation range for the chip 50 needs to bedetermined in advance when the measurement is made by the camera 300 orthe like as shown in FIG. 9. The evaluation range 21 is of the same sizeas the island of the light shielding film 20 in FIG. 1 and the like.That is, the strictest specification is that there is no chip 50 ofglass in the range sized to 2.6 mm in the long side direction of theopposing substrate and 0.2 mm in the short side direction, namely thedepth. The loosest specification is that there is no chip 50 of glass ina range of 1.3 mm in the long side direction of the opposing substrateand 0.1 mm in the short side direction, namely the depth.

FIG. 15 is a perspective view showing the range of the black matrix 220in the periphery of the liquid crystal display panel in a case ofdividing the mother substrate by the separation line 40 shown in FIG.14. With the measurement of the chip 50 using the camera 300 or the likeshown in FIG. 9, the range 21 in FIG. 15 will be measured. Although theboundary is indicated by the islands of the range 21 in FIG. 15, such aboundary is not indicated on an actual product, and therefore it isnecessary to set a measuring device to measure inside a predeterminedarea.

Although the range 21 of the light shielding film is indicated in FIG.15 assuming a case of forming the chamfer 10 on the top surface 210 sideof the opposing substrate 200 or on the bottom surface side of the TFTsubstrate 100, the configuration is not limited to this but the accurateand rapid evaluation of the chip 50 can also be performed only bysetting the range inside the black matrix 220 when the chamfer 10 isformed on the short side of the opposing substrate 200 and/or TFTsubstrate 100.

The length of the long side to be inspected may be in the range of 0.3to 10 mm depending on the thickness or a property of the glass, a cycletime, a customer's demand, or the like.

The invention claimed is:
 1. A liquid crystal display device sandwichingliquid crystal between a first substrate having a rectangular plane witha TFT and a pixel electrode formed thereon in a matrix form and a secondsubstrate having a rectangular plane with a color filter formed thereon,wherein a long side of the first substrate is longer than a long side ofthe second substrate, the long side of the first substrate or the secondsubstrate is chamfered, and the first substrate has a light shieldingregion made of metal, the light shielding region is disposed in theplace overlapping with the chamfered area of the first substrate or thesecond substrate, and a size of the light shielding region is between1.3 mm and 2.6 mm along the long side of the first substrate or thesecond substrate and between 0.1 mm and 0.2 mm along a short sidedirection of the first substrate or the second substrate.
 2. The liquidcrystal display device according to claim 1, wherein there is no chip ona top surface of the chamfered area overlapping with the light shieldingregion.
 3. The liquid crystal display device according to claim 1,wherein the light shielding region is covered by sealing materialbonding the first substrate to the second substrate.